Aiming at the problem that the energy consumption of UAV(unmanned aerial vehicle) with high visual range and high maneuverability characteristics in the air ground efficient data communication system assisted by MEC(mobile edge computing) of UAV with high visual range and high mobility characteristics has a direct impact on the communication quality and multi-user and multi service requirements, a alternating iterative optimization method was proposed to minimize the system energy consumption on the premise of ensuring user experience. By establishing a UAV-MEC network system containing five sub models of UAV trajectory, channel model, local computing model, computing unloading model and UAV energy consumption, the UAV trajectory, user unloading volume and UAV power were jointly optimized. The system energy consumption was optimized. The simulation results show that compared with existing benchmark schemes, the computational energy consumption of end users reduce by 35%, and the overall performance of the system is improved.